Eating Meat May Raise Colon Cancer Risk

May 23, 2011 -- Red meat and processed meat may increase the risk of developing colon cancer, according to a new report from the American Institute for Cancer Research (AICR) and the World Cancer Research Fund.

The report, which builds on the two groups' 2007 Continuous Update Project, points to solid evidence that eating less red meat and avoiding processed meat altogether can slash colon cancer risk.

When this advice is combined with other diet and lifestyle changes -- such as consuming less alcohol, boosting fiber intake, exercising, and maintaining a healthy body weight -- it could prevent 45% of all colon cancer cases, or more than 64,000 cases of colon cancer each year, the report states.

Colorectal cancer is the third most common type of cancer diagnosed in the U.S., excluding skin cancers, according to the American Cancer Society.

"The good news is that we have some control over our colon cancer risk," says Elisa Bandera, MD, PhD, an associate professor of epidemiology, Cancer Institute of New Jersey, New Brunswick. Bandera was a member of the expert panel that analyzed all of the available literature on colon cancer risk, diet, exercise, and weight.

Eating less than 18 ounces per week of red meat, such as beef, lamb, or pork, shows very little increase in colon cancer risk, the report states.

People who eat 3.5 ounces or red meat every day (24.5 ounces per week) will have a 17% increased risk of colon cancer compared to someone who eats no red meat, according to the report. People who eat 7 ounces per day (49 ounces per week) will have a 34% increased risk.

People who eat 3.5 ounces of processed meat a day will have a 36% increased risk of developing colon cancer compared with people who avoid all processed meat, according to the report. The more processed meat eaten, the higher your risk for developing colorectal cancer.

Why Meat May Raise Colon Cancer Risk

Exactly how red and/or processed meat increases risk for colon cancer isn't clear, but there are several theories. Some research suggests that chemicals called heterocyclicamines,which are produced when meat is cooked at high temperature, may play a role. Processed meats are made by smoking, curing, salting, and or adding preservatives such as nitrates. The body converts nitrates into nitrosamines, which are known to increase risk of cancer.

"It appears that red meat -- and maybe processed meat even more -- has some relationship with colon cancer risk," says panel member Steven H Zeisel, MD, PhD, theKenan Distinguished Professor of nutrition and pediatrics at the University of North Carolina, Chapel Hill.

"A betting person would say there is risk associated with the consumption of red meat and processed meat," he says. "Moderating the amount of red meat you take in is reasonable based on this data. And trying to cut back and substitute other types of meat or vegetables would be a good idea for someone who wants to reduce risk of colon cancer."

Diet and Lifestyle Changes

Drinking alcohol may increase colon cancer risk, according to the report. The report also states that excess belly fat may raise colorectal cancer risk, but staying lean, eating more fiber, and engaging in regular physical activity can help lower this risk.

"If you limit consumption of red meat, you have more room on your plate for good things like whole grains and vegetables," Bandera says. Some simple substitutes can help. "Choosing brown rice instead of white rice is a good way of increasing fiber."

Alice Bender, MS, RD, of the AICR, says the new report is especially important to people with a family history of colorectal cancer.

"If you have family history, it's more important than ever to follow these guidelines because they offer potentially some extra protection," she says.

National Cattlemen's Beef Association Weighs In

"Americans should continue to build healthier diets with beef, knowing the scientific evidence to support the role of nutrient-rich, lean beef in a healthy, balanced diet is strong," says Shalene McNeill, PhD, RD, executive director of Human Nutrition Research at the National Cattlemen's Beef Association.

"Nothing in this update should change the way Americans consume beef," she says. " In fact, Americans are consuming beef well within WCRF's [World Cancer Research Fund] 500 gram (18 ounces) per week recommendation. As a scientist, registered dietitian, and a mother, I will continue to recommend lean beef to Americans trying to build a healthier plate because of the unique package of nutrients and enjoyment it brings to a healthy diet."